The Australian Computer Emergency Response Team issued an advisory Thursday warning companies that their wireless networks
could be disrupted by an attacker with a handheld device.

A vulnerability in the most common wireless networking protocol, the 802.11 standard established by the Institute of Electrical and
Electronic Engineers (IEEE), allows a device to essentially jam other devices on a network using a low-power signal.

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"Previously, attacks against the availability of IEEE 802.11 networks
have required specialized hardware and relied on the ability to saturate
the wireless frequency with high-power radiation, an avenue not open to discreet attack," AusCERT said in its advisory. "This vulnerability makes a successful, low-cost attack against a wireless network feasible for a semiskilled attacker."

The flaw affects the clear channel assessment (CCA) procedure, which
attempts to minimize the probability that two devices will broadcast on the same frequency. The attack can cause all devices in range to wait to
transmit until the attack has halted.

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The attack is considered a denial-of-service tactic and, as such, is not rated a critical problem. However, AusCERT warns that emergency response
networks should move to wireless technologies that are not vulnerable to jamming.

Vulnerable devices include any that support the 802.11, 802.11b and
low-speed 802.11g wireless standards. Devices that use 802.11a or
high-speed 802.11g, above 20mbps, are not vulnerable, the organization
said.